The inclusion of electron correlation in intermolecular potentials:: applications to the formamide dimer and liquid formamide
The inclusion of electron correlation in intermolecular potentials:: applications to the formamide dimer and liquid formamide
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DOI：
10.1007/s002140000180
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发表时间：
2000-11-01
影响因子：
1.7
通讯作者：
Karlström, G
中科院分区：
文献类型：
--
作者：
Brdarski, S;Åstrand, PO;Karlström, G
通过计算二阶 Moller-Plesset (MP2) 理论水平的分子偶极矩和极化率，对甲酰胺的非经验分子轨道 (NEMO) 势中使用的静电性质和极化率的质量进行了测试。 MP2 水平下的分子偶极矩比 Hartree-Fock (HF) 水平下的分子偶极矩低 11%，而通过添加电子相关性和使用相当大的基组，极化率的各向同性部分增加了 36%。在 HF 水平上获得的原子电荷、偶极矩和极化率经过重新调整，以获得 MP2 水平上的正确分子特性。甲酰胺环状二聚体的最低电势为 -17.50 kcal/mol，具有 MP2 标度特性，并且明显低于其他给出的电势。构建了两个分子间势并用于后续的分子动力学模拟：一个具有常规 NEMO 势，另一个具有重新调整的 MP2 属性。目前的 NEMO 模型中包含短分子间距离静电场的阻尼。 MP2 尺度模型的液体甲酰胺的平均能量较低，与实验结果非常吻合。 MP2 尺度势的模拟能量降低表明液体甲酰胺中存在强色散相互作用。
A test of the quality of the electrostatic properties and polarizabilities used in the nonempirical molecular orbital (NEMO) potential is carried out for formamide by calculating the molecular dipole moment and polarizability at the second-order Moller-Plesset (MP2) level of theory. The molecular dipole moment is 11% lower at the MP2 level than at the Hartree-Fock (HF) level, whereas the isotropic part of the polarizability is increased by 36% by adding electron correlation and using a considerably larger basis set. The atomic charges, dipole moments and polarizabilities obtained at the HF level are rescaled to get the correct molecular properties at the MP2 level. The potential minimum for the cyclic dimer of formamide is -17.50 kcal/mol with the MP2-scaled properties and is significantly lower than other potentials give. Two intermolecular potentials are constructed and used in subsequent molecular dynamics simulations: one with the regular NEMO potential and the other with the rescaled MP2 properties. A damping of the electrostatic field at short intermolecular distances is included in the present NEMO model. The average energies for liquid formamide are lower for the MP2-scaled model and are in good agreement with experimental results. The lowering of the simulation energy for the MP2-scaled potential indicates the strong dispersive interactions in liquid formamide.